Background: Post-operative nausea and vomiting (PONV) are the most common unpleasant experiences following laparoscopic surgeries.

Objectives: In the current research, compared the effect of dexamethasone and ondansetrone combined and separately on preventing nausea and vomiting in the patients undergone elective surgery with general anesthetic using laparoscopic cholecystectomy procedure.

Patients and Methods: One hundred fifty patients with ASA class I and II aged between 20-65 years voluntarily participated in this double-blind randomized prospective study. The patients were randomly divided into three groups of 50. All the participants faced general anesthetic procedure whereas each group received different treatment regimen as follow: the O-group, 4 mg ondansetrone, the D-group, 8 mg dexamethasone, and the OD –group, combination of 4 mg of ondansetrone plus 8 mg dexamethasone. Every episode of PONV and the need for antiemetic drug were evaluated 6 hours following the operation and then every 6 hours up to 24 hours after the operation. The complete response was defined as the case with no episode of PONV within the 24 hours and the need for anti-vomiting cases was defined as the failure in prophylaxis.

Results: The complete response was observed in 62.2, 68.2 and 89.6 percent of O, D, and OD groups, respectively. The frequency of complete response was significantly lower in OD-group (P = 0.011 vs. the D and P = 0.005 vs. the O group). The need for the antiemetic drug in groups O, D, and OD was 28.3, 22.8, and 6.2, respectively. The incidence of vomiting and failure in prophylaxis was observed in D-group during the first six hrs. The highest need for the anti-vomiting drug within the 6 to 24 hours of post operation was observed in group O compared to the group OD (P = 0.012).

Conclusions: Combination of dexamethasone and ondansetrone is more effective than the treatment of PONV by each of these drugs separately following the laparoscopic cholecystectomy .The application of dexamethasone alone in preventing premature PONV is less effective than the application of ondansetrone or the combination of these two drugs. In addition, ondansetrone alone is less effective than the combination of these two drugs in preventing PONV.